1. Field of the Invention
The present invention relates to a method of coating three dimensional and non-uniform objects with molecular sieves using pulsed laser deposition.
2. Description of Related Art
There are a variety of methods for fabricating molecular sieves into thin films. A popular approach is the seed method, which involves the deposition of colloidal suspensions of zeolite nanosols onto a flat substrate followed by a controlled secondary growth of the nanoparticles. The resulting films are generally continuous and sometimes oriented. It appears, however, that the seed method works best with only a few types of zeolites, especially those with crystal morphologies that efficiently pack on the substrate surface such as zeolite NaA or ZSM-5. This also implies that this method works best on flat surfaces. Consequently, there are relatively few examples of zeolite films and no examples of oriented films on non-planar surfaces.
The deposition-during-synthesis technique has been used to grow zeolite Beta onto macroporous alumina spheres with a 4% loading by immersing the support in the synthesis mixture. Analogously, metal and ceramic monoliths have also been coated with zeolite Beta, Mordenite, and ZSM-5 utilizing this technique. Molecular sieve films prepared by the direct deposition of crystals from solution, however, often suffer from defects and poor adhesion. Furthermore, controlling the film thickness and orientation can be quite a challenge.